  <div class="container">
    <button>
      <span id="u">u</span><span id="n">n</span><span id="i">i</span><span id="v">v</span><span id="e">e</span><span id="r">r</span><span id="s">s</span><span id="ee">e</span>
    </button>
      <div class="moon"></div>
  </div>

<style>
/* From Uiverse.io by iDamjan - Tags: button */
button {
  z-index: 500;
  box-shadow: rgba(124, 172, 226, 0.295) 2px 2px 8px;
  width: 15rem;
  height: 4rem;
  letter-spacing: 0.5rem;
  border: none;
  border-radius: 0.1rem;
  color: white;
  animation: universe-is-moving 2s infinite ease-out;
  background: linear-gradient(
    90deg,
    rgba(185, 43, 39, 1) 0%,
    rgba(21, 101, 192, 1) 100%
  );
  background-size: 200% 200%;
  animation-direction: alternate;
  background-position: 0% 100%;
  animation-name: universe-is-moving;
  animation-duration: 1.8s;
  animation-iteration-count: infinite;
  animation-timing-function: linear;
  transition: all 0.5s ease-in-out;
}

button:hover {
  border-radius: 2rem;
  cursor: pointer;
}

.moon {
  position: relative;
  left: 2rem;
  bottom: -2rem;
  right: 0;
  width: 20px;
  height: 20px;
  transform: translate3d(42px, -62px, -135px);
  background-color: rgba(255, 255, 255, 0.76);
  border-radius: 50%;
  animation: 3s  universe-moon infinite ease-in-out;
  animation-timing-function: linear;
}

#u {
  font-size: 1.2rem;
  animation: 3s ease-in-out universe-letters-are-moving infinite;
}

#n {
  font-size: 1.2rem;
  animation: 3s ease-in-out universe-letters-are-moving infinite;
  animation-delay: 200ms;
}

#i {
  font-size: 1.2rem;
  animation: 3s ease-in-out universe-letters-are-moving infinite;
  animation-delay: 400ms;
}

#v {
  font-size: 1.2rem;
  animation: 3s ease-in-out universe-letters-are-moving infinite;
  animation-delay: 600ms;
}

#e {
  font-size: 1.2rem;
  animation: 3s ease-in-out universe-letters-are-moving infinite;
  animation-delay: 800ms;
}

#r {
  font-size: 1.2rem;
  animation: 3s ease-in-out universe-letters-are-moving infinite;
  animation-delay: 1000ms;
}

#s {
  font-size: 1.2rem;
  animation: 3s ease-in-out universe-letters-are-moving infinite;
  animation-delay: 1200ms;
}

#e {
  font-size: 1.2rem;
  animation: 3s ease-in-out universe-letters-are-moving infinite;
  animation-delay: 1400ms;
}

#ee {
  font-size: 1.2rem;
  animation: 3s ease-in-out universe-letters-are-moving infinite;
  animation-delay: 1600ms;
}

@keyframes universe-is-moving {
  from {
    background-position: 0% 100%;
  }

  to {
    background-position: 100% 0%;
  }
}

@keyframes universe-letters-are-moving {
  0% {
    font-size: 1.2rem;
  }

  50% {
    font-size: 1.5rem;
  }

  100% {
    font-size: 1.2rem;
  }
}

@keyframes universe-moon {
  0% {
    z-index: 5;
    transform: translateY(-8em) translateX(10em);
  }

  50% {
    transform: translateX(0.5em) translateY(-1em);
  }

  100% {
    transform: translateY(-8em) translateX(10em);
    z-index: -5;
  }
}

</style>
